A comparative study was made of the influence of atomic-scale surface steps upon dislocation nucleation at crystal surfaces based upon an all atom method and a hierarchal multi-scale approach. The multi-scale approach was based upon the variational boundary integral formulation of the Peierls-Nabarro dislocation model in which interatomic layer potentials derived from atomic calculations of generalized stacking fault energy surfaces were incorporated. The nucleation of screw dislocations in these 2 body-centered cubic material systems, subjected to a simple shear stress, was studied. As compared to dislocation nucleation from perfectly flat surfaces, the presence of atomic-scale surface steps rapidly reduced the critical stress for dislocation nucleation by almost an order of magnitude as the step height increased. In addition, they could influence the slip planes on which dislocation nucleation occurred. The results of the all atom method and the multi-scale approach were in good agreement, even for steps with height of only a single atomic layer. Such corroboration supported the further use of the multi-scale approach to study dislocation nucleation phenomena in more realistic geometries of technological importance, which were beyond the reach of all current atom simulations.

Corroboration of a Multiscale Approach with All Atom Calculations in Analysis of Dislocation Nucleation from Surface Steps. D.E.Segall, C.Li, G.Xu: Philosophical Magazine, 2006, 86[32], 5083-101